1. Field of the Invention
The present invention concerns generally concerns the construction of vehicles such as snowmobiles, all terrain vehicles (“ATVs”), and other similar vehicles. More specifically, the present invention concerns the construction of a frame for such vehicles.
2. Description of the Related Art
Snowmobiles, ATVs, and related vehicles (hereinafter, “recreational vehicles,” although the appellation should not be construed to be limited only to the vehicles or type of vehicles described herein) often function under similar operating conditions. Despite this, snowmobiles, ATVs, and other recreational vehicles do not share a common design approach or a commonality of components. This is due, in large part, to the different stresses and strains (mainly at the extremes) that the different vehicles experience during routine operation.
As a general rule, the prior art includes few, if any, examples of a common design approach to ATVs and snowmobiles. Primarily, this appears to be due to the fact that these vehicles were designed traditionally from two radically different starting points.
Snowmobile frames traditionally have been constructed with a tunnel and an engine cradle, which are individual elements made from metal, plate-like elements, as shown in FIG. 4. ATV frames, on the other hand, have been constructed in much the same way as motorcycle frames by connecting a number of tubular frame elements to one another.
In the case of snowmobiles, the tunnel and engine cradle combination (referred to herein as the “frame” or “frame assembly”) traditionally has been made of a very strong but light-weight material such as aluminum. To withstand the forces encountered under normal operating conditions, the individual plate elements of the tunnel and engine cradle have been relatively thick so that they do not bend or buckle under high loads. Unfortunately, this adds significantly to the overall weight of the vehicle.
Moreover, several holes need to be provided at various locations in the engine cradle to accommodate shafts for the drive axle, the transmission, and the gearbox. Traditionally, the holes have been drilled into the engine cradle after its construction. A problem with this construction technique is that the holes may not line up as precisely as the manufacturer would like. In some cases, the manufacturer must expend considerable resources to align these shaft holes before producing the final vehicle product.